/Engine/Source/Runtime/Slate/Public/Widgets/Layout/SWidgetSwitcher.h
Gets the slot index of the specified widget.
The slot index, or INDEX_NONE if the widget does not exist.
int32 GetWidgetIndex ( [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > Widget ) const